Erosional event causing gas-venting on the upper continental slope, Campos Basin, Brazil

During lowstand of sea level of the Last Glacial Maximum the south-flowing Brazil Current carved a terrace on the upper continental slope of Campos Basin, Brazil. The removal of approximately 40 m of the sediment column is inferred from in situ geotechnical measurements. This erosional event was able to expose the shallow (∼10 m) methane generation zone to the seafloor. As a consequence of the methane oxidation process, carbonate concretions, nodules and crusts of dominantly dolomitic composition were precipitated with characteristic light δ13C and heavy δ18O isotope values. Seaward of this erosional zone on the slope, where sediments are preserved, no nodules were encountered.